1. Field of the Invention
The present invention relates to new photoresist compositions that are suitable for short wavelength imaging, including sub-300 nm and sub-200 nm such as 248 nm, 193 nm and 157 nm. Photoresists of the invention can exhibit significant adhesion to SiON and other inorganic surface layers. Preferred photoresists of the invention contain a resin with photoacid-labile groups, one or more photoacid generator compounds, and an adhesion-promoting additive compound.
2. Background
Photoresists are photosensitive films used for transfer of images to a substrate. A coating layer of a photoresist is formed on a substrate and the photoresist layer is then exposed through a photomask to a source of activating radiation. The photomask has areas that are opaque to activating radiation and other areas that are transparent to activating radiation. Exposure to activating radiation provides a photoinduced chemical transformation of the photoresist coating to thereby transfer the pattern of the photomask to the photoresist-coated substrate. Following exposure, the photoresist is developed to provide a relief image that permits selective processing of a substrate.
A photoresist can be either positive-acting or negative-acting. For most negative-acting photoresists, those coating layer portions that are exposed to activating radiation polymerize or crosslink in a reaction between a photoactive compound and polymerizable reagents of the photoresist composition. Consequently, the exposed coating portions are rendered less soluble in a developer solution than unexposed portions. For a positive-acting photoresist, exposed portions are rendered more soluble in a developer solution while areas not exposed remain comparatively less developer soluble.
While currently available photoresists are suitable for many applications, current resists also can exhibit significant shortcomings, particularly in high performance applications such as formation of highly resolved sub-quarter micron and sub-tenth micron features.
Consequently, interest has increased in photoresists that can be photoimaged with short wavelength radiation, including exposure radiation of below 300 nm such as 248 nm, or even 200 nm or less such as 193 nm. Quite recently, F2 excimer laser imaging, i.e. imaging with radiation having a wavelength of about 157 nm, has been considered as a route to manufacture of even smaller features. See, generally, Kunz et al., SPIE Proceedings (Advances in Resist Technology), vol. 3678, pages 13–23 (1999).
Silicon oxynitride (SiON) layers and other inorganics such as Si3N4 coatings have been employed in semiconductor device manufacture, for example as an etch stop layer and an inorganic antireflective layer. See, for instance, U.S. Pat. Nos. 6,124,217; 6,153,504; and 6,245,682.
It would be desirable to have new photoresist compositions that could be imaged at short wavelengths such as sub-300 nm and sub-200 nm. It would be particularly desirable to have such photoresists that would provide good resolution on SiON and other inorganic substrate layers.